This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. xc2xa7119 from my two applications entitled Light Emitting Module And Compatible Optical Pickup Device Adopting The Same, respectively filed with the Korean Industrial Property Office on the 19th day of April 1999 and there duly assigned Ser. No. 13806/1999, and on the 20th day of July 1999 and there duly assigned Ser. No. 29279/1999.
1. Field of the Invention
The present invention relates to a light emitting module for emitting a laser light beam and a compatible optical pickup device conforming to the light emitting module, and more particularly, to a light emitting module in which two light sources respectively emitting two light beams of different wavelengths are packaged into a single module, and to a compatible optical pickup device conforming to the light emitting module so that recording media of different formats can be compatibly used.
2. Description of the Related Art
DVD players and DVD-ROM drives are noted in the video and audio field for their high density recording/reproducing capabilities. Optical pickup devices are typically used in compact disk (i.e., CD) players, CD-ROM drives, digital versatile disk (i.e., DVD) players, and DVD-ROM drives to record information onto and to read and reproduce information from the recording medium in a non-contact manner (i.e., the head writes and reads information without touching the surface of the recording medium). To provide compatibility, an optical pickup device that is incorporated into a DVD player should be able to record onto and reproduce information from not only DVDs, but also the compact disk family of recordable media such as CDs, CD-Rs (i.e., CD-recordable), CD-RWs (i.e., CD-rewritable), CD-Is (i.e., CD-interactive) and CD-Gs (i.e., CD graphics). The thickness of a DVD is standardized by a different specification than the thickness of other recordable media within the CD family due to the allowance of error in disk inclination and the numerical aperture of the objective lens. That is, the thickness of the disk for the existing family of compact disks is 1.2 millimeters while the thickness of a DVD is 0.6 millimeters. When an optical pickup device that is designed for a DVD is used for with a recordable medium from the CD family, spherical aberration occurs due to this significant difference in thicknesses. The spherical aberration not only reduces the intensity of light to levels that are insufficient in intensity to record information signals, but also causes a deterioration of the signals that are read from the recording medium.
DVD""s are standardized differently from the CD family of recordable media. The wavelength of a reproduction light source for the existing family of compact disks is about 780 nanometers while the wavelength of a reproduction light source for a DVD is about 650 nanometers. Thus, typical CD players are not able to reproduce information that has been recorded on a DVD due to differences in the wavelengths of the light used for reproduction and the occurrence of spherical aberration. We have noticed that there is a need to develop abetter optical pickup device for DVDs, and to make optical pickup devices for DVDs compatible with the existing family of compact disks.
To solve the above problems, recent efforts in the art, some of which are described in detail below in conjunction with FIGS. 1 and 2, to provide a conventional compatible optical pickup device are apt to use one optical module emitting a light ray having a 650 nm wavelength toward a relatively thin disk such as a DVD, and a second optical module emitting a light ray having a 780 nm wavelength toward a relatively thick disk such as a compact disk with the CD family of media disks. These efforts have sought to construct compatible pickups with two discrete, separately sited and individually adjustable first and second optical modules that are aligned with a photodetector. The photodetector must be adjusted so that reproduction of servo and radio frequency signals is possible. One optical module is set to emit light at a 650 nm wavelength and to direct that light to be reflected by an optical disk after passing one, or more, beam splitters and an objective lens, towards a photodetector. Then, the other optical module is adjusted so that the light being emitted is reflected by the optical disk and then accurately focused onto the photodetector. We have observed that conventional compatible optical pickup devices are deficient in several aspects. First, at least one of the first optical module, the second optical module and the photodetector must be adjusted. Consequently, assembly of optical pickups is inconvenient and the rate of defects attributable to the assembly increases. Second, miniaturization of the optical pickup is difficult because the first and second optical modules are in separate locations. Third, two monitoring photodetectors are necessary to adjust the optical output of each light source; this unduly complicates the wiring of the accompanying circuit.
Accordingly, it is an object to the present invention to provide an improved light emitting process and structure.
It is another object to provide a light emitting process that facilitates compatible optical communication with different formats between an emitter and photodetector. for so that recording media of different formats can be compatibly used.
It is still another object to provide a light emitting process, light emitter and photodetector that facilitates optical communication enabling compatible use of recording media with different formats.
It is yet another object to provide a light emitting module having an improved structure and simplified optical configuration, with a reduction in the number of parts, and a compatible optical pickup device compatible with the module.
It is a further object to provide an optical process and apparatus able to reproduce information from both the family of contemporary compact disks and with digital versatile disks.
It is a still further object to provide an optical process and apparatus that is compatible with the different wavelengths used to read information stored on different types of recordable media, while minimizing the affects of spherical aberration.
It is a yet further object to provide an optical process and apparatus that maybe miniaturized, and that lends itself to easy, error-free assembly.
These and other objects maybe attained with a light emitting module constructed with abase, first and second emitting light sources installed on the base that emit laser beams in different wavelength regions, and a beam splitter that divides the beams emitted from the first and second light sources. A photodetector monitors the optical outputs from the first and second light sources by receiving the beams emitted from the first and second light sources after their division by the beam splitter.
The principles of the present invention also contemplate a compatible optical pickup device that may be constructed with a light emitting module constructed with a base, first and second light emitting sources installed on the base that emit laser beams in different wavelength regions, a beam splitter that divides the beams emitted from the first and second light sources, and a monitoring photodetector that receives the beams from the first and second light sources via the beam splitter. An objective lens disposed with the optical path between the light emitting module and an optical recording medium, focuses the beams emitted from the first and second light sources onto the optical recording medium, and an optical path converting device that is disposed within the optical path between the light emitting module and the objective lens, converts the proceeding path of an incident beam. A photodetector receives the beams that are emitted from the first and second light sources, reflected from the optical recording medium and input via the optical path converting device.